The ground-breaking experiments of [1]} and [2]} showed the complex topological features of the surface waves formed on the jet. They revealed that these waves are responsible for the transition from laminar to turbulent flow, and found underlying similarities of the occurring instabilities to inviscid linear theory. [3]} with their pioneering experiments scrutinised the various stages of the jet dynamics: from the growth of linear modes (through a Kelvin-Helmholtz instability) that characterises the early-time dynamics, to the development of nonlinearities leading to `primary' and subsequent `secondary' breakup events (through long filament pinchoff modulated by a Rayleigh-Taylor instability), and the formation of a cascade of droplet sizes. These authors found that mean droplet-size is proportional to the wavelength selected during the Rayleigh–Taylor instability (also observed by [4]}). In the same premise, [5]} showed that the droplet size distribution is also a function of the nozzle geometry and the surrounding pressure. More recently, [6]} presented the results of an experimental study of the spatial evolution of turbulent immiscible liquid-liquid jets; however, a detailed account of the spatio-temporal development, and critical mechanisms leading to droplet generation remains outstanding.
